Workers evacuated the building after the warning shots. It was not clear whether there were any casualties.

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8 p.m.

Israel's military says it is prepared to step up its efforts against Palestinian militants in the Gaza Strip if rocket fire at Israel continues.

Lt. Col. Jonathan Conricus, a military spokesman, said Monday that Israel has boosted forces near the Gaza border with additional infantry troops, defensive systems and intelligence units.

Conricus told reporters that the army has so far struck more than 30 targets belonging to the Palestinian militant groups Hamas and Islamic Jihad.

He says some 200 rockets have struck Israel in the past three hours.

He says Hamas is "bringing destruction upon the Gaza Strip."

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6:10 p.m.

Palestinian health officials say Israeli airstrikes in the northern Gaza Strip have killed two people and wounded another three.

It was not immediately clear if the casualties were militants or civilians. Health officials said they were all men in their 20s.

Israel launched the airstrikes on Monday in response to an intense barrage of rocket fire from Gaza.

The rocket attack from Gaza appeared to be an act of revenge after a botched Israeli raid the day before killed seven Palestinian militants.

Israeli Prime Minister Benjamin Netanyahu was meeting with his military chief and defense minister late Monday.

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5:25 p.m.

The Israeli military says it has dispatched fighter jets to strike "terror targets" throughout Gaza following a barrage of mortar and rocket fire that wounded six people.

Palestinian militants fired dozens of rockets into southern Israel at sundown Monday, a day after an Israeli military raid in Gaza left seven militants and an Israeli officer dead.

Gaza's Hamas rulers and the smaller Islamic Jihad group claimed joint responsibility for the rocket barrage.

Israeli media say six people were wounded by Palestinian fire, including a 19-year-old who was critically hurt when a mortar shell hit a bus.

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5:15 p.m.

Israeli medics say a 19-year-old man has been critically wounded in an explosion in southern Israel.

The man apparently sustained the wounds in a Palestinian mortar attack from Gaza that struck a bus.

Black smoke could be seen billowing into the air from the area of the mortar strike.

The incoming fire comes a day after an Israeli undercover military raid in Gaza sparked fighting that left seven Palestinian militants and an Israeli officer dead.

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5 p.m.

The Israeli military says a bus has been hit by fire from the Gaza Strip as air raid sirens sound throughout southern Israel.

The incoming fire comes a day after an Israeli undercover military raid in Gaza sparked fighting that left seven Palestinian militants and an Israeli officer dead.

There were no immediate details on injuries from Monday's strike on the Israeli bus.

Rockets could be seen being launched out of Gaza toward Israel, and Israel's Iron Dome rocket defense system was heard deploying.

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7:30 a.m.

The Israeli military says an officer was killed and another was moderately wounded during an operation in southeast Gaza Strip, involving an exchange of gunfire.

The early Monday statement followed a rare late-night burst of violence in which seven Palestinians were also killed. The flare-up came as Israel and Gaza's Hamas rulers had appeared to be making progress toward ratcheting down months of border violence.